Town CLIMATE RISK

Stornoway Flood Risk Data

Stornoway is a town, within the Na h-Eileanan Siar council area. The settlement runs to the UK coastline. LocalRisk has flood, heat, air and ground-stability data for 265 postcodes in Stornoway; 12 samples are linked at the foot of this page.

10.2% of postcodes in Stornoway fall into SEPA's high flood-risk band - slightly above the UK average of about 7%. The band reflects the highest flood risk within each postcode; some properties may face little or no direct flood risk. A further 4.5% sit in the medium band; 85.3% are lower-risk. Across the wider Na h-Eileanan Siar council area the figure is 23.6%, so Stornoway runs lower than its parent council. Two postcodes a few streets apart can land in different bands; what drives the gap is elevation, distance to the nearest watercourse, and how the surrounding drainage performs in heavy rain. The postcode list at the foot of this page links to the full address-level reading for each postcode in Stornoway.

Met Office UKCP18 projections (50th percentile) estimate around 2 days above 25°C per year across the Na h-Eileanan Siar area, averaged over the 2021-2040 period under the RCP8.5 high emissions scenario. These are probabilistic projections - the 50th percentile is the central estimate within RCP8.5; the full range of modelled outcomes is wide and lower emissions scenarios would produce lower figures. Heat exposure within Stornoway varies by property orientation and construction, but the overall heat stress level is relatively low. The headline 2-day figure is a council-level UKCP18 estimate (LAD resolution), not a property-level reading.

Annual mean PM2.5 across the Na h-Eileanan Siar area is 3.1 µg/m³ - close to the World Health Organisation guideline of 5 µg/m³. Within Stornoway, readings are not flat: postcodes within 200 metres of an A-road or major junction routinely run 30-50% higher during weekday rush hours than residential streets two roads back. The figure is a council-level Defra UK-AIR estimate (1km modelled grid).

Ground stability in Stornoway follows the underlying geology more than the postal boundary. The British Geological Survey GeoSure dataset maps clay shrink-swell risk on a 50-metre cell, and properties on the same street can sit in different bands where a clay seam ends mid-road. Pre-1980 housing on clay-rich ground is the most exposed; properties on bedrock or well-drained sandy soils are typically lower-risk. A postcode-level check picks up that variation.

A free postcode check on LocalRisk covers up to six hazards for any address in Stornoway: SEPA flood mapping, BGS ground stability, Met Office heat projections, Defra PM2.5, plus coastal erosion and green-space access where relevant. The postcode list below opens an address-level report for each postcode in Stornoway; the council link at the top of this page returns to the wider Na h-Eileanan Siar picture.